The present invention relates to a molding machine and, more particularly, to a molding machine in which compressed air is passed through molding sand filled in a molding flask to consolidate the thin layer of the molding sand covering over the surface of a pattern and then a squeeze operation is applied to the whole part of the molding sand in the mold flask.
Such molding machines have been known, which comprise a vertically movable table carrying a pattern having a large number of bores communicating with the ambient air, a molding flask with an upset frame, if necessary mounted on the table, a cover means closing the upper opening of the molding flask or the upset frame and provided with an air supply port, and means for supplying compressed air through the air supply port so that the compressed air then flows through the molding sand and is discharged through the bores of the pattern, whereby the molding sand in the molding flask and the upset frame is consolidated and compacted by the air so as to form a mold.
In this type of molding machine, a closed space is defined by the cooperation of the pattern, the molding flask, the upset frame and the cover means closing the upper opening of the upset frame. As the compressed air is introduced into this closed space, the cover means are inconveniently floated and lifted by the force exerted by the compressed air. In such a case, a clearance is formed between the cover means and the molding flask or the upset frame to allow the compressed air to escape therethrough to the outside.
Therefore, the clamp cylinder which is arranged to push the cover means against the upper surface of the molding flask or the upset frame, is required to have a large enough capacity to withstand this floating or lifting force. Therefore such a molding machine has various inconveniences such as enlargement of the size of the machine, complication of the mechanism and so forth.